The overall objectives of the proposed investigation are: 1) to obtain pertinent information concerning the mechanism of important enzymatic reactions of natural organic compounds related to steroid hormones, and 2) to explore, in conjunction with the synthesis of putative biosynthetic intermediates and their related compounds, recently developed synthetic methods as well as to develop the technology with which relatively restricted synthetic reactions can be applied to the modification of highly functionalized compounds. We propose as specific aims: (1) to continue the investigation of the mechanism of the cholesterol side-chain cleavage reactions between C-20 and 22 using adrenal cortex P-450; (2) to synthesize 20- or 22- aza derivatives of ecdysones, insect molting hormones, and study their biological activities using insects with a view towards producing possible insect growth inhibitors; (3) to establish the stereochemical course of the enzymatic oxidation reaction of steroid methyl groups using chiral C-19 methyl steroids; and (4) to investigate the stereochemical mechanism of the reduction of steroid double bonds. Furthermore, the absolute stereochemistry of one of the most important precursors of steroid hormones, presqualene, will be examined. Throughout these studies, the sophisticated use of modern spectroscopy including C-13 nmr and the exciton chirality circular dichroism method will be required. These studies will provide significant information regarding the mechanism of biological oxidation and reduction.